I have some Aulonocara Stuartgranti Usisya fry, there was 49 of them, they are in a bare bottom 20L with a sponge filter, fed once a day Repashy Super Foods powder, and I do a 50% WC every week. But, Lately, while watching the tank, I'll see one or two swimming kinda strangely, and in the next day or two, they are dead. I'm down to 44 now with another one not lookin so good. Anyone know whats goin on? I'm really confused!